A tunnel in Avantra is used when a connection between two Gateways is only possible in one direction, that is when Gateway A can connect to Gateway B but Gateway B cannot connect to Gateway A.
Technically, Gateway A keeps alive a connection to Gateway B, which allows Gateway B to send data to Gateway A without actually having to establish a connection to Gateway A.
Avantra uses intelligent objects monitoring. It watches for critical trends rather than for single events. A single shortdump in an SAP System is not considered critical. A certain number of shortdumps over a given period of time is indeed considered critical. We call this Trend Analysis, and it greatly reduces the number of false alerts.